Organosilicate resins as hardmasks for organic polymer dielectrics in fabrication of microelectronic devices

ABSTRACT

This invention is a method comprising providing a substrate, forming a first layer on the substrate, wherein the first layer has a dielectric constant of less than 3.0 and comprises an organic polymer, applying an organosilicate resin over the first layer, removing a portion of the organosilicate resin to expose a portion of the first layer, and removing the exposed portions of the first layer. The invention is also an integrated circuit article comprising an active substrate containing transistors and an electrical interconnect structure containing a pattern of metal lines separated, at least partially, by layers or regions of an organic polymeric material having a dielectric constant of less than 3.0 and further comprising a layer of an organosilicate resin above at least one layer of the organic polymer material.

[0001] This application claims priority to U.S. provisional applicationSer. No. 60/226,170 filed Aug. 21, 2000 and No. 60/284,317 filed Apr.17, 2001.

FIELD OF THE INVENTION

[0002] This invention relates to the fabrication of microelectronicdevices having organic polymeric dielectric materials and, morespecifically, to the use of organosilicate resins as hardmasks (oretchstops) in the fabrication of such devices.

BACKGROUND OF THE INVENTION

[0003] The microelectronics fabrication industry is moving towardsmaller geometries in its devices to enable lower power consumption andfaster device speeds. As the conductor lines become finer and moreclosely packed, the requirements of the dielectrics between suchconductors become more stringent. New materials having a lowerdielectric constant than the dielectric constant for silicon dioxide,the traditionally used dielectric material, are being investigated.Among the dielectric materials that are attaining increased acceptanceare spin-on, organic polymers having a dielectric constant of less thanabout 3.0. Polyarylenes, including polyarylene ethers and SiLK™semiconductor dielectric (from The Dow Chemical Company), are theprimary organic polymeric dielectrics being considered.

[0004] The fabrication of microelectronic devices using these newdielectric materials is being reviewed. See, e.g., “Material ResearchSociety (MRS) Bulletin, Oct 1997, Volume 22, Number 10” To date,however, the polyarylene dielectrics generally have been patterned inthe traditional manner using inorganic hardmasks in forming patterns inthe dielectric materials. Typically, the polyarylene dielectric isapplied to the substrate and cured, followed by vapor deposition of aninorganic hardmask. A pattern is formed in the inorganic hardmaskaccording to standard patterning practices, e.g., application of aphotoresist (i.e., softmask), followed by exposure and development ofthe softmask, pattern transfer from the softmask into the hardmask, andremoval of the softmask. Etching of the hardmask is typically done usingfluorine based chemistries. The underlying polyarylene dielectric canthen be patterned. Deposition conditions must be carefully monitored toassure adequate adhesion between the hardmask and the polyarylene films.

[0005] Subsequent to the original priority date claimed by thisapplication, patent publications were made that also discuss variousmethods and embodiments of dielectric materials, etch stops andhardmasks in fabrication of microelectronic devices.

[0006] In WO01/18861 (Mar. 15, 2001), after stating the well knownconcept that layers used as adjacent etchstop and dielectric materialsshould have substantially different etch selectivities, the applicantsteach that an inorganic layer (defined as containing no carbon atoms)should be used as a via level and metal level intermetal dielectric andan organic low dielectric constant material should be used between theinorganic layers as an etch stop material.

[0007] In WO00/75979 (Dec. 14, 2000), teaches a structure having a firstdielectric layer which is an organic polymer and a second dielectriclayer over the first layer which is a organohydridosiloxane made by arelatively complex synthesis method.

[0008] In addition, U.S. Pat. No. 6,218,078 (Apr. 17, 2001 filed Sep.24, 1997) teaches the use of a spin on hardmask (onlyhydrogensilsesquioxane is mentioned) over a low dielectric constantpolymer (only benzocyclobutene is mentioned).

[0009] Finally, U.S. Pat. 6,218,317 (Apr. 17, 2001 filed Apr. 19, 1999)teaches use of methylated oxide hardmasks over polymeric interlayerdielectric materials. This patent mentions the benefits that bothhardmask and ILD can be spin-coated.

SUMMARY OF THE INVENTION

[0010] The Inventors have discovered an improved method that wouldreduce the need for vapor deposition of inorganic hardmasks. Dependingon the specific integration scheme used, this reduction or eliminationcould reduce costs and improve performance and yield due to eliminationof the need to take the wafer off the spin track for vapor deposition ofthe hardmask, potentially lower effective dielectric constant in thedevice when the hardmask is an embedded hardmask (or etchstop) due tothe lower dielectric constants of the organosilicates compared tostandard inorganic hardmasks, and potential additional processimprovements when the hardmask is photodefinable.

[0011] Thus, according to a first embodiment this invention is a methodcomprising

[0012] providing a substrate,

[0013] forming a first layer on the substrate, wherein the first layerhas a dielectric constant of less than 3.0 and comprises an organicpolymer,

[0014] applying an organosilicate resin over the first layer,

[0015] removing a portion of the organosilicate resin to expose aportion of the first layer, and

[0016] removing the exposed portions of the first layer. Preferably, theorganosilicate resin is selected from oligomers and polymers based on adivinyl siloxane bis benzocyclobutene type monomer or from hydrolyzedalkoxy or acyloxysilanes.

[0017] Optionally, the organosilicate resin can be removed after imagingof the first layer. According to a second option a second layer of a lowdielectric constant organic polymer is applied over the organosilicatelayer. In this configuration, the organosilicate functions as a buriedetch stop to control precisely the depth of trench in a dual damasceneintegration scheme. The buried etch stop may have areas removed bylithography where vias will penetrate into the first organic polymerdielectric layer. The etching of the buried etchstop layer may occurbefore or after coating of the second organic polymer layer dependingupon what type of integration scheme is selected.

[0018] The invention is also an integrated circuit article comprising anactive substrate containing transistors and an electrical interconnectstructure containing a pattern of metal lines separated, at leastpartially, by layers or regions having a dielectric constant of lessthan 3.0 and comprising an organic polymer, wherein the article furthercomprises a layer of an organosilicate resin above at least one layer ofthe organic polymer material.

[0019] Moreover, the Inventors have discovered that not allorganosilicates are equally compatible with the various organic polymerdielectrics used as the interlayer dielectrics. Particularly, for usewith low dielectric organic arene polymers based on Diels Alderchemistry or that may otherwise have ethylenic unsaturation, thefollowing formulation is very useful as either a hardmask, etchstop, or,even adhesion promoting layer. Thus, according to a third embodimentthis invention is a composition comprising hydrolyzed or partiallyhydrolyzed reaction products of:

[0020] (a) an alkoxy or acyloxy silane having at least one groupcontaining ethylenic unsaturation which group is bonded to the siliconatom

[0021] (b) an alkoxy or acyloxy silane having at least one groupcontaining an aromatic ring which group is bonded to the silicon atom,and

[0022] (c) optionally an alkoxy or acyloxy silane having at least onegroup which is a C₁-C₆ alkyl, which is bonded to the silicon atom.

[0023] According to a fourth embodiment this invention is an articlecomprising two layers in direct contact with each other the first layerbeing an arene polymer having ethylenic unsaturation and the secondlayer being the composition according to the third embodiment or thecured product of such a composition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 and FIG. 2 are cross section representations showingexemplary integration schemes using the hard mask materials of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The first layer is a material having a low dielectric constantand is formed primarily from an organic polymer, which makes up at leastthe majority of the first layer. As used herein, “organic polymer” meansa polymer, which has primarily carbon in its backbone of the polymerchain, but may also include heteroatoms, such as oxygen (e.g.,polyarylene ethers) or nitrogen (see, e.g., polyimides as described inThin Film Multichip Modules, pp. 104-122, International Society forHybrid Microelectronics, 1992). The organic polymer may contain smallamounts of Si in the backbone but are, more preferably, free oressentially free of Si in the backbone. The first layer may containpores. These pores may be helpful in further reducing the dielectricconstant of the material. The layer may also contain adhesion promoters(including Si containing adhesion promoters), coating aids, and/orresidual materials left after forming the pores. The amount of suchadditional components found in the first layer is preferably relativelysmall amounts, e.g., less than 10 percent by weight, preferably lessthan 1 percent by weight, most preferably less than 0.1 percent byweight.

[0026] Preferably, the first layer is either a porous or non-porouspolyarylene. Examples of polyarylenes include SiLK semiconductordielectric, poly(arylene ethers) (e.g., PAE™ resins from Air Products)as described in EP 0 755 957 B1, Jun. 5, 1999 and/or the Flare™ resinsmade by Allied Signal Corp. (see N. H. Hendricks and K. S. Y Liu, Polym.Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1996, 37(1), p. 150-1; also,J. S. Drage, et al., Material Res. Soc., Symp. Proc. (1997), Volume 476,(Low Dielectric Constant Materials III), pp. 121-128 and those describedin U.S. Pat. Nos. 5,115,082; 5,155,175; 5,179,188 and 5,874,516 and inPCT WO91/09081; WO97/01593 and EP 0755957-81). Alternatively, the firstlayer may be formed with the cross-linked polyphenylenes, as disclosedin WO97/10193.

[0027] Most preferably, however, the polyarylene is one of thosedisclosed in U.S. Pat. No. 5,965,679, incorporated herein by reference.Preferred polyarylenes are the reaction product of a cyclopentadienonefunctional and acetylene functional compound. The polymers arepreferably the cured or cross-linked product of oligomers of the generalformula:

[A]_(w)[B]_(z)[EG]_(v)

[0028] wherein A has the structure:

[0029] and B has the structure:

[0030] wherein EG are end groups having one or more of the structures:

[0031] wherein R¹ and R² are independently H or an unsubstituted orinertly-substituted aromatic moiety and Ar¹, Ar² and Ar³ areindependently an unsubstituted aromatic moiety or inertly-substitutedaromatic moiety, M is a bond, and y is an integer of three or more, p isthe number of unreacted acetylene groups in the given mer unit, r is oneless than the number of reacted acetylene groups in the given mer unitand p+r=y−1, z is an integer from 1 to about 1000; w is an integer from0 to about 1000 and v is an integer of two or more.

[0032] Such oligomers and polymers can be prepared by reacting abiscyclopentadienone, an aromatic acetylene containing three or moreacetylene moieties and, optionally, a polyfunctional compound containingtwo aromatic acetylene moieties. Such a reaction may be represented bythe reaction of compounds of the formulas

[0033] (a) a biscyclopentadienone of the formula:

[0034] (b) a polyfunctional acetylene of the formula:

[0035] (c) and, optionally, a diacetylene of the formula:

[0036] wherein R¹, R², Ar¹, Ar², Ar³ and y are as previously defined.

[0037] The definition of aromatic moiety includes phenyl, polyaromaticand fused aromatic moieties. “Inertly-substituted” means the substituentgroups are essentially inert to the cyclopentadienone and acetylenepolymerization reactions and do not readily react under the conditionsof use of the cured polymer in microelectronic devices withenvironmental species, such as water. Such substituent groups include,for example, F, Cl, Br, —CF₃, —OCH₃, —OCF₃, —O—Ph and alkyl of from oneto eight carbon atoms, cycloalkyl of from three to about eight carbonatoms. For example, the moieties which can be unsubstituted orinertly-substituted aromatic moieties include:

[0038] wherein Z can be: —O—, —S—, alkylene, —CF₂—, —CH₂—, —O—CF₂-,perfluoroalkyl, perfluoroalkoxy,

[0039] wherein each R³ is independently —H, —CH₃, —CH₂CH₃, —(CH₂)₂CH₃ orPh. Ph is phenyl.

[0040] A second preferred class of organic polymers are the reactionproducts of compounds of the formula:

(R—C≡C—)_(n)—Ar—L[—Ar(—C≡C—R)_(m)]_(q)

[0041] wherein each Ar is an aromatic group or inertly-substitutedaromatic group and each Ar comprises at least one aromatic ring; each Ris independently hydrogen, an alkyl, aryl or inertly-substituted alkylor aryl group; L is a covalent bond or a group which links one Ar to atleast one other Ar; n and m are integers of at least 2; and q is aninteger of at least 1, and wherein at least two of the ethynylic groupson at least one of the aromatic rings are ortho to one another.Preferablv these polvmers have the formula:

[0042] The organosilicate resin may be the hydrolyzed or partiallyhydrolyzed reaction products of substituted alkoxysilanes or substitutedacyloxysilanes (see, e.g., U.S. Pat. No. 5,994,489 and WO00/11096,incorporated herein by reference) or may be the cured products of suchsilanes. Preferably, the hydrolyzed reaction products are applied andthen cured during the fabrication process.

[0043] Hydrolysis of alkoxy or acyloxysilanes produces a mixture ofnonhydrolyzed, partially hydrolyzed, fully hydrolyzed and oligomerizedalkoxy silanes or acyloxysilanes. Oligomerization occurs when ahydrolyzed or partially hydrolyzed alkoxysilane or acyloxysilane reactswith another alkoxysilane or acyloxysilane to produce water, alcohol oracid and a Si—O—Si bond. As used herein, the term “hydrolyzedalkoxysilane” or “hydrolyzed acyloxysilane” encompasses any level ofhydrolysis, partial or full, as well as oligomerized. The substitutedalkoxy or acyloxy silane prior to hydrolysis is preferably of theformula:

[0044] wherein R is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or adirect bond; Y is C₁-C₆ alkyl, C₂-C₆ alkenyl, a C₂₋₆ alkynyl, a C₆-C₂₀aryl, 3-methacryloxy, 3-acryloxy, 3-aminoethylamino, 3-amino, —SiZ₂OR′,or —OR′; R′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Z is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—OR′. The term “alkylidene” refers to aliphatic hydrocarbon radicalswherein attachment occurs on the same carbon. The term “alkylene” refersto radicals, which correspond to the formula —(C_(n)H_(2n))—. The term“aryl” refers to an aromatic radical, “aromatic” being defined ascontaining (4n+2) electrons, as described in Morrison and Boyd, OrganicChemistry, 3rd Ed., 1973. The term “arylene” refers to an aryl radicalhaving two points of attachment. The term “alkyl” refers to saturatedaliphatic groups, such as methyl, ethyl, etc. “Alkenyl” refers to alkylgroups containing at least one double bond, such as ethylene, butylene,etc. “Alkynyl” refers to alkyl groups containing at least one carbon tocarbon triple bond. “Acyl” refers to a group having —C(O)R structure(e.g., a C₂ acyl would be —C(O)CH₃). “Acyloxy” refers to groups having—OC(O)R structure. The groups previously described may also containother substituents, such as halogens, alkyl groups, aryl groups, andhetero groups, such as ethers, oximino, esters, amides; or acidic orbasic moieties, i.e., carboxylic, epoxy, amino, sulfonic, or mercapto,provided the alkoxysilane remains compatible with the other componentsof the coating composition. Preferably, the silanes used are mixtures ofsilanes. The silanes may be alkoxy silane, acyloxy silane,trialkoxy-silanes, triacetoxysilanes, dialkoxysilanes, diacetoxysilanes,tetraalkyoxysilane or tetra-acetoxysilanes. Examples of some of theorganic groups directly attached to the silicon atom may be such thingsas phenyl, methyl, ethyl, ethacryloxypropyl, aminopropyl,3-aminoethylaminopropyl, vinyl, benzyl, bicycloheptenyl,cyclohexenylethyl, cyclohexyl, cyclopentadienylpropyl, 7-octa-1-enyl,phenethyl, allyl or acetoxy. The silanes are preferably hydrolyzed orpartially hydrolyzed by a solventless process The silanes will retainorganic portions even after cure provided some organic groups are bondeddirectly to the silicon atom. In order to balance desired properties inthe hardmask or etchstop layer, a mixture of silanes may be used. Forexample, applicants have found that use of an aryl alkoxy or arylacyloxy silane (such as, phenyltrimethoxy silane) in combination with analkyloxysilane or acyloxysilane having a group with unsaturatedcarbon-carbon bonds (e.g. alkenyl or alkyidenyl moieties such as vinylor phenyethynyl) provides excellent wetting, coating and adhesionproperties with the preferred organic polymeric dielectric materials,particularly those aromatic polymers which have additional carbon-carbonbond unsaturation. The presence of the aromatic substituted silane alsoimproves moisture sensitivity and may improve dielectric constant oversingle silane systems. Furthermore, using alkylalkoxy silanes or alkylacyloxy silanes (such as methyltrimethoxysilane orethyltrimethoxysilane) in combination with the aryl and unsaturatedsubstituted silanes has been found to further improve moistureretention/exclusion and reduce dielectric constant in the resultingfilm. Furthermore, a mixture of monoalkoxy, monoacyloxy, dialkoxy,diacyloxy, trialkoxy, triacyloxy, tetraalkoxy silanes or tetraacyloxysilanes may be used in the mixtures as well to enable enhancement ofetch selectivity, adjustment of branching, etc.

[0045] The hydrolyzed reaction products of such mixtures of silanes areone embodiment of this invention. Particularly, preferred is thefollowing composition which is the hydrolzyed or partially hydrolyzedproduct of a mixture comprising

[0046] (a) 50-95 mole % silanes of the formula

[0047] wherein Ra is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or adirect bond; Ya is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl , C₆-C₂₀aryl, 3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino,—SiZa₂ORa′, or —ORa′; Ra′ is independently, in each occurrence, a C₁-C₆alkyl or C₂-C₆ acyl; and Za is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl,C₆₋₂₀ aryl, or —ORa′, provided at least one of Za or the combinationRa—Ya comprises a.non-aromatic carbon carbon bond unsaturation,

[0048] (b) 5 to 40 mole percent

[0049] wherein Rb is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or adirect bond; Yb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆-C₂₀aryl, 3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino,—SiZb₂ORb′, or —ORb′; Rb′ is independently, in each occurrence, a C₁-C₆alkyl or C₂-C₆ acyl; and Zb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl,C₆₋₂₀ aryl, or —ORb′, provided at least one of Zb or the combination ofRb—Yb comprises an aromatic ring, and.

[0050] (c) 0 to 45 mole percent

[0051] wherein Rc is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or adirect bond; Yc is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆-C₂₀aryl, 3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino,-SiZc₂ORc′, or —ORc′; Rc′ is independently, in each occurrence, a C₁-C₆alkyl or C₂-C₆ acyl; and Zc is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-₆ alkynyl,C₆₋₂₀ aryl, or —ORc′, provided at least one of Zc or the combination ofRc—Yc comprises an alkenyl. The mole percent is based on total moles ofsilanes (a), (b) and (c) present. These organosilanes based on mixturesmay be useful as hardmasks, etchstops or adhesion promoters infabrication of microelectronic devices particularly with the preferredorganic dielectric polymer layers that may have carbon carbonunsaturation.

[0052] The manufacture of the hydrolyzed organosilane composition can beadjusted to give the properties desired, such as control of molecularweight, polymer architecture (e.g. block copolymers, random copolymers,etc.) When combinations of organosilanes are used and one of theorganosilanes is significantly more reactive than the other, theInventors have found that it is preferable to continuously add the morereactive species . during the hydrolysis reaction. This ensures that theresiduals of both types of silanes are more uniformly distributedthroughout the resulting oligomer or polymer. The rate of addition isadjusted to provide the desired mixture of residuals of the silanes inthe resulting polymer. As used herein, “continuously add” means that thecharge of the reactive silane is not added all at once put is ratheradded in several uniform portions or, more preferably is poured or addedgradually at a desired addition rate. In addition, adding the watercontinuously during the hydrloysis reaction also facilitates control ofmolecular weight. The amount of water added in the hydrolysis may alsobe important. If too little water is used, gellation may occur. If toomuch water is used, phase separation may occur. For the preferredcompositions, 1-3 moles of water per mole of silane, more preferably1.5-2.5 moles of water per mole of silane may be added.

[0053] Other suitable organosilicate resins are resins based onbenzocyclobutene chemistry. The preferred organosiloxane is made frommonomers of the formula:

[0054] wherein

[0055] each R³ is independently an alkyl group of 1-6 carbon atoms,trimethylsilyl, methoxy or chloro; preferably R³ is hydrogen;

[0056] each R⁴ is independently a divalent, ethylenically unsaturatedorganic group, preferably an alkenyl of 1 to 6 carbons, most preferably—CH₂═CH₂—;

[0057] each R⁵ is independently hydrogen, an alkyl group of 1 to 6carbon atoms, cycloalkyl, aralkyl or phenyl; preferably R⁵ is methyl;

[0058] each R⁶ is independently hydrogen, alkyl of 1 to 6 carbon atoms,chloro or cyano, preferably hydrogen;

[0059] n is an integer of 1 or more;

[0060] and each q is an integer of 0 to 3.

[0061] The preferred organosiloxane bridged bisbenzocyclobutene monomerscan be prepared by methods disclosed, for example, in U.S. Pat. Nos.4,812,588; 5,136,069; 5,138,081 and WO94/25903.

[0062] Suitable oligomeric benzocyclobutene based siloxanes areavailable from The Dow Chemical Company under the tradename CYCLOTENE™.These materials have the benefit of themselves having a low dielectricconstant of about 2.65 and, thus, could be left in the microelectronicdevice as embedded hardmasks without significant deleterious effect tothe performance of the device. The hydrolyzed silanes previouslymentioned also have a dielectric constant lower than 4, which is thevalue of the dielectric constant for silicon oxide which, currently, iscommonly used. Silicon nitride is also commonly used and has adielectric constant of about 7.The silanes also are highly thermallystable and, thus, can withstand rigorous fabrication processingconditions.

[0063] The substrate is preferably an electrically active substrate thatincludes, preferably, a semiconducting material, such as a siliconwafer, silicon-on-insulator, or gallium/arsenide. Preferably, thesubstrate includes transistors. The substrate may include earlierapplied layers of metal interconnects and/or electrically insulatingmaterials. These electrically insulating materials may be organicpolymers as discussed above or could be other known dielectrics, such assilicon oxides, fluorinated silicon oxides, silicon nitrides,silsesquioxanes, etc. The earlier applied metal interconnects may haveraised features, in which case the organic polymer or its precursor mustbe capable of filling the gaps between these features.

[0064] The organic polymeric dielectric is applied to the substrate byany known method that can achieve the desired thickness. Preferably, anuncured polymer or oligomer of the organic polymer is spin coated from asolvent system at spin speeds of 500 to 5000 rpm. The thickness of theorganic polymer layer is preferably less than 5000 nm, more preferablyabout 50 to about 2000 nm. Suitable solvents include mesitylene,pyridine, triethylamine, N-methylpyrrolidinone (NMP), methyl benzoate,ethyl benzoate, butyl benzoate, cyclopentanone, cyclohexanone,cycloheptanone, cyclooctanone, cyclohexylpyrrolidinone, and ethers orhydroxy ethers, such as dibenzylethers, diglyme, triglyme, diethyleneglycol ethyl ether, diethylene glycol methyl ether, dipropylene glycolmethyl ether, dipropylene glycol dimethyl ether, propylene glycol phenylether, propylene glycol methyl ether, tripropylene glycol methyl ether,toluene, xylene, benzene, dipropylene glycol monomethyl ether acetate,dichlorobenzene, propylene carbonate, naphthalene, diphenyl ether,butyrolactone, dimethylacetamide, dimethylformamide and mixturesthereof.

[0065] The remaining liquid is then removed from the coating and theoligomer, or uncured polymer, is preferably cured by heating.Preferably, an initial heating step occurs on a hot plate under nitrogenat atmosphere, followed by a second high temperature cure on a hotplateor in a furnace. Cure temperatures for the preferred polyarylenes,disclosed in U.S. Pat. No. 5,965,679, are in the range of 50° C. to 600°C., more preferably 100 to 450° C., for 0.1 to 60 minutes. In makingporous first layers, special steps may need to be provided to burn outor otherwise remove a porogen. See, e.g., WO00/31183, incorporatedherein by reference.

[0066] After applying (the application step may include a bake step toremove residual solvent) and, optionally, curing the first layer, theorganosilicate material is applied. Any known coating process may beused, such as vapor deposition of monomers, spin coating, dip coating,spray coating, etc. However, spin coating of an oligomer or lowmolecular weight polymer solution is preferred. The thickness of theorganosilicate layer is preferably greater than 50 Angstroms (5 nm),more preferably greater than 100 Angstroms. Preferably, the layer has athickness of less than about 1000 Angstroms for a top hardmask and lessthan about 500 Angstroms for an embedded hardmask. According to a firstembodiment, the organosilicate material is cured, preferably attemperatures of 50 to 500, more preferably 100 to 400° C. for 0.1 to 60minutes. The precise temperatures will depend on the organosilicatematerial selected. A photoresist is applied over the organosilicatematerial. The photoresist is imaged and developed according toconventional methods to remove a portion of the photoresist exposing apattern on the hardmask. The organosilicate hardmask may then be etchedto expose a portion of the first layer dielectric. Etching of theorganosilicate hardmask may occur by variety of methods, such as wetetch (e.g., electrochemical, photoelectrochemical or open circuitetching) or dry etch (e.g., vapor, plasma, laserbeam, e-beam, ion)techniques as described in Etching in Microsystems, Michael Kohler,Wiley-VCH. The photoresist may be removed during etching or in aseparate removal step. The exposed portion of the first dielectric layermay then be etched by such methods as wet or dry etching to form atrench, via or other desired feature. If desired, a second organicpolymer layer may then be applied and cured over the patternedorganosilicate layer. A second hardmask of any type, but preferablyagain an organosilicate, may be applied over the second organic polymerlayer and patterned according to standard processes. The organic polymercan then be etched down to the embedded hardmask or etch stop and wherea pattern has been opened in the embedded hardmask, down through thefirst layer of organic polymer.

[0067] According to a second embodiment, a curable organosilicateformulation (e.g., b-staged or partially cured oligomer or hydrolyzed orpartially hydrolyzed organosilane) includes a photoactive agent such asa photoinitiator that initiates further cure or cross-linking of thecurable polymer. Examples of such compounds include peroxides, azocompounds and benzoin derivatives. Photoactive, spin-coatableformulations of BCB based organosilicates are commercially availablefrom The Dow Chemical Company under the trade name CYCLOTENE 4000series. Alternatively, the system could be a positive system comprisinga photoactive compound and a separate dissolution inhibitor or,preferably a dissolution inhibitor, which itself is photoactive.Non-limiting examples of suitable photosensitive, dissolution inhibitingcompositions/compounds include sulfonyl esters of trihydroxybenzophenone(for example, THBP) and cumyl phenol. In this case, after applying theorganosilicate and removing excess solvent, the organosilicate hardmaskis exposed to activating wavelengths of radiation and developed to leavea pattern of hardmask on the organic polymer layer. As a result, the useof a photoactive agent can result in either positive or negativeexposure properties. Positive means that the photoinitiator cross-linksupon exposure, negative means that the photoinitiator breaks bonds uponexposure. Suitable developers are known in the art and includehydrocarbons, glycols, glycol ethers, substituted aromatic solvents, andmixtures thereof. The hardmask is then cured as in the first embodiment.After curing, the exposed organic polymer layer may be etched as in thefirst embodiment.

[0068] According to a third embodiment, after being applied over a firstorganic polymer dielectric layer, the organosilicate material is cured,preferably at temperatures of 50 to 500° C., more preferably 100 to 400°C. for 0.1 to 60 minutes. The precise temperatures will depend on theorganosilicate material selected. A second layer of the organic polymerdielectric can then be applied by any of the coating methods previouslymentioned and a full or partial cure of the organic polymer layercompleted. A variety of dual damascene processes can be used toconstruct both trench and via structures using the embeddedorganosilicate layer as an etch stop to control the uniformity, depth,and/or shape of the trenches. The organosilicate hardmask may then beetched to expose a portion of the first layer dielectric. Etching of theorganosilicate hardmask may occur by variety of methods, such as wetetch (e.g., electrochemical, photoelectrochemical or open circuitetching) or dry etch (e.g., vapor, plasma, laserbeam, e-beam, ion) etchtechniques as described in Etching in Microsystems, Michael Kohler,Wiley-VCH. The exposed portion of the first dielectric layer may then beetched by such methods as wet or dry etching to create a via or otherdesired feature.

[0069] Examples of some dual damascene processes that may be usedinclude the following:

[0070] Scheme 1: a non-sacrificial hardmask is used as an embeddedhardmask and a single top hardmask is used, via patterning at via level.In this scheme, the via level dielectric is deposited followed byapplication of the embedded hardmask layer and subsequent applicationand patterning of a photoresist. A copper diffusion barrier may beapplied under the dieletric layer, in which case the diffusion barrierwill also have to be etched at an appropriate point in the process toenable formation of the connection to the metal vias. The integrationcan continue by one of the following options: Option 1: Etch of hardmaskonly; Option 2: Full etch of hardmask and partial etch of dielectric;Option 3: Full etch of hardmask and dielectrics; Option 4: full etch ofhardmask, dielectric and diffusion barrier. The photoresist is removedand the trench level dielectric is applied followed by a top hardmaskand application and patterning of a photoresist. The structure is thenetched down to substrate level where a via channel has been made or downto the embedded hardmask where that hardmask was not previouslypatterned.

[0071] Scheme 2: In scheme 2 the following layers are applied to thesubstrate in order: diffusion barrier, via level dielectric, embeddedhardmask, trench level dielectric, trench hardmask and patternedphotoresist. The trench hard mask is then etched to desired trenchprofile. Via patterned photoresist is then applied and via etch occursaccording to one of the following options: Option 1: via profile etchedonly through trench dielectric to top of embedded hardmask, followed byetch of the embedded hardmask, followed by etch of trench and via;Option 2: via profile etched through the trench dielectric and embeddedhardmask followed by etch of trench and via; Option 3: via profileetched all the way to substrate followed by etch of remaining trenchprofile.

[0072] Scheme 3: In this scheme the following layers are applied to thesubstrate in order: diffusion barrier, via level dielectric, embeddedhardmask, trench level dielectric, trench hardmask and patternedphotoresist. The trench hard mask is then etched to desired via profile.The next etch step can continue to form the via profile down to anylayer desired in the stack. The top hardmask is then etched for trenchprofile and the remaining etch of the trench and via are performed.

[0073] Scheme 4 resembles scheme 2 except a dual top hardmask is used.

[0074] Scheme 5 resembles scheme 3 except a dual top hardmask is used.

[0075] Schemes 6-8 resemble schemes 1-3, respectively, but are enabledby the use of a photodefmable, embedded hardmask such as is taught inthis patent document. As such no photoresist is required to image theembedded hardmask.

[0076] Schemes 9 and 10 resemble schemes 4 and 5 but all hardmasks arephotodefinable.

[0077] Scheme 11 does not use an embedded hardmask but rather uses dualtop hardmask and time etch to form via and trench. Either the trench orthe via profile may be formed first.

[0078] Scheme 12 is similar to scheme 11 but uses a photodefmablehardmask for at least one of the dual top hardmask layers.

[0079] Schemes 13-24 are the same as schemes 1-12, but the top hardmasksare removed rather than remaining in the stack.

[0080] In schemes 1-24 the metallization occurs after via and trenchformation and may include use of barrier materials as is known in theart.

[0081] In using schemes 1-24 with this invention, at least one of thehardmask layers is an organosilicate as defined herein and one of thedielectric layers is an organic polymer. Variations on these proceduresfor use of the organosilicate hardmask with organic polymericdielectrics are considered within the scope of this invention. Forexample, after etching a pattern in the organic polymeric dielectric,metal interconnects may be added by known processes. For example, withcopper interconnects a liner material, such as a tantalum, titanium,tantalum based alloys, titanium based alloys, and tungsten based alloysmay be applied by physical vapor, thermal, chemical or plasma assistedvapor deposition. A copper seed layer may also be applied by physical,thermal, plasma assisted vapor, electroless or electroplated depositionfollowed by electroplating of copper metal. If the interconnect systemis subsequently annealed at a sufficiently high temperature (greaterthan 200° C.), a benzocyclobutene (BCB) based organosilicate hardmaskwill begin to degrade and may be easily cleaned off with a weak acid,for example. Alternatively, a tungsten plug could be formed in a via byknown methods.

[0082] Chemical mechanical polishing to enhance planarization and/orremove surface layers or features may also be used according to knownmethods. Cleaning steps to remove photoresists and other residual layersmay also be used as is known.

[0083] Note that since the organosilicate hardmask itself has a lowdielectric constant it may be convenient to use it as an embeddedhardmask, which is not removed from the article, but rather hasadditional interconnect/dielectric layers applied over it.Alternatively, the organosilicate hardmask may be removed by any knownprocess, e.g. oxygen/solvent treatment, thermal degradation plus solventcleaning, etc.

[0084] One important factor that enables the organosilicate resin to beused as a hardmask for the organic polymer dielectrics is thatorganosilicate resins are relatively resistant to the chemistries usedto etch the organic polymer dielectrics. Etch selectivity can be definedas the thickness of the organic polymer dielectric divided by thethickness of organosilicate removed when exposed to the same etchchemistry. According to this invention, preferably an etch selectivityof at least 3, more preferably at least 5, is present. For thehydrolyzed silanes, etch selectivity may be higher—on the order ofgreater than 10, preferably greater than 20. Etch selectivities can beincreased by performing treatments, such as exposure to fluorinatedplasmas, and irradiation with light or e-beams on the BCB basedorganosilicates.

[0085] Some of the benefits of the present invention become clearer whenexamined in the form of some specific examples.

[0086] One approach uses a non-sacrificial (i.e., the layer is notremoved but rather becomes a permanent part of the device),non-photodefinable organosilicate. This allows for the replacement of avapor phase deposited hardmask with a low permittivity spin-on depositedhardmask. Standard patterning practices still apply. An improvement inperformance in the device is obtained due to a decrease in the combineddielectric constant of the multilayered dielectric stack. The relativepermittivity of the spin on hardmask of this invention is between 3.2,preferably 3.0, and 1.8 and compared to standard vapor phase hardmaskshaving a relative permittivity between 9 and 3.0. Secondly, a costreduction is obtained due to the lower cost-of-ownership intrinsic tospin-on dielectrics.

[0087] A second approach uses a sacrificial (i.e., the layer isremoved), non- photodefinable organosilicate resin. Standard patterningpractices still apply. After the patterning step, a dedicated processingstep involving, for example, an oxygen and solvent treatment is used toremove the sacrificial spin-on hardmask. Due to the removal of thislayer, the lowest possible dielectric constant is obtained. An increasein yield and reliability is obtained due to a decrease in number ofinterfaces in the multilevel build.

[0088] A third approach uses a non-sacrificial, photodefinableorganosilicate. In addition to the benefits noted in the first approach,an increase in yield is anticipated due to the lowered probability ofprocessing induced defects. Also, the need for photoresists andsoftmasks is reduced or eliminated.

[0089] A fourth approach uses a sacrificial, photodefinableorganosilicate. The benefits noted in the second approach still applywith the added benefits of an increase in yield due to the loweredprobability of processing-induced defects and simplification of theprocessing due to elimination of the need for the photoresists orsoftmasks.

[0090] Additional variations on the method of this invention areexemplified by the following procedures.

[0091] Referring to FIG. 1, on a substrate 10, is coated polyarylene 20,e.g., SiLK™ I semiconductor dielectric, which is then cured. Onto thecured polyarylene 20 is coated an organosilicate 30, which is also thencured. Onto the organosilicate 30, an inorganic hardmask 40 may be vapordeposited. A photoresist is coated onto inorganic hardmask 40 and imagedand developed and the hardmask 40 is then etched and the remainingphotoresist removed by cleaning to reveal a pattern 41 of a trench inthe inorganic hardmask 40. A second photoresist layer is applied,exposed and developed and the organosilicate 30 is etched. The remainingphotoresist is again removed to reveal a pattern 31 of a via in theorganosilicate 30. Referring to FIG. 1d, a via 21 is etched in theorganic polymer, followed by a change of etch chemistry to a chemistrythat will etch through the organosilicate and use of a timed etch toform the trench 22. Hardmask 40 may be removed at this time byconventional removal methods. Post etch cleans may be used beforedepositing a liner 50, copper seed and electroplating copper 60 onto thesubstrate. The copper 60 may be chemically mechanically polished toplanarize as shown in 1 f. The copper may then be annealed at hightemperature and the organosilicate resin easily removed by a weak acidclean. If desired, a cap layer 70 may be deposited and the stepsrepeated to provide additional layers.

[0092] Referring to FIG. 2, on a substrate 10, is coated polyarylene 20,which is then cured. A photoactive organosilicate 32, e.g., CYCLOTENE4022 photodefmable BCB based resin, is applied and solvent is removed.The photoactive organosilicate is imagewise exposed to activatingwavelengths of radiation and the unexposed portions are removed to forma via pattern 33. The remaining organosilicate 32 is then cured. Asecond photoactive organosilicate 34 is applied, exposed and developedto form a trench pattern 35, followed by cure of the organosilicate 34.A non-fluorine gas can be used to etch the via 21 followed by afluorinated gas etch to remove the organosilicate hardmask 34 and formthe trench 22. The metalization steps may then be formed as recited inconnection with FIG. 1.

[0093] As mentioned previously, the process of the present invention canbe used in dual damascene fabrication. For example, the substrate is asubtractive or damascene interconnect structure. A vapor depositedinorganic film (Si_(x)O_(y), Si_(x)O_(y)N_(z), Si_(x)N_(y), Si_(x)C_(y),Si_(x)O_(y)C_(z)) is applied, followed by application of the organicpolymer (e.g., SiLK resin) film, which is baked and cured. An optionalembedded etch stop layer can be applied (e.g., a vapor phase depositedlayer or more preferably an organosilicate film as recited in thispatent document, which can optionally be photo-defmable). The embeddedmask can be patterned using conventional techniques. Next, a secondorganic polymer film is applied, which is baked and cured. On top of thesecond organic polymer film, a dual hardmask strategy may implemented,wherein one of the films is an organosilicate film and the other is aninorganic Si_(x)O_(y), Si_(x)O_(y)N_(z), Si_(x)N_(y), Si_(x)C_(y),Si_(x)O_(y)C_(z), or metallic (e.g., Ta, TaN, Ti, TiN, TiSiN, TaSi, WN,WSIN) film. The four approaches of photodefmable, non-photo defmable,sacrificial, and non-sacrificial organosilicate layers apply here, aswell.

[0094] The sequence used to transfer the resist patterns or exposed anddeveloped organosilicate patterns for via and trench into the organicpolymer film can be done according to the via first and trench level,full or partial etch of via first at trench level, trench first attrench level, full or partial etch of trench at trench level, or viafirst or full or partial etch of via at via level, depending on the useof an embedded hardmask. Once the pattern is transferred into the SiLKfilm, conventional methods for metallization apply.

[0095] This invention applies to subtractive fabrication methods as wellas damascene methods. For subtractive methods, the substrate consists ofpatterned metal features manufactured by conventional technology. In agap-filling version, the organic polymer resin (e.g., SiLK Hsemiconductor dielectric) is required and is deposited by any applicabletechnique and undergoes a bake and cure step resulting in theevaporation of the solvents and densification of the organic polymerfilm. The organic polymer film can optionally be mechanically chemicallypolished or etched (using resist etch back, polymer etch back or anyother related methodology) to obtain a globally planarized film. Thislast step can be postponed. On the organic polymer film, theorganosilicate (OS) film can be deposited by the methods describedabove. Again, the organosilicate can be sacrificial or non-sacrificial,and photodefmable or non-photodefinable as is described more fullybelow:

[0096] Option a: The organosilicate film is non sacrificial and notphoto-definable.

[0097] A resist pattern is applied on the OS film and this pattern istransferred into the OS film by dry etching techniques. Subsequently,the organic polymer film is patterned by conventional means as describedearlier using the patterned film as a template.

[0098] Option b: The organosilicate film is sacrificial and notphoto-defmable.

[0099] A resist pattern is applied on the OS film and this pattern istransferred into the OS film by dry etching techniques. Subsequently,the organic polymer film is patterned by conventional means, asdescribed earlier, using the patterned OS film as template. After theorganic polymer film has been patterned, the OS film is removed bydissolving in an acid or by dry etching or by chemical mechanicalpolishing

[0100] Option c: The organosilicate film is non sacrificial andphoto-definable.

[0101] The OS film is exposed and developed, as described earlier, andthis pattern is transferred into the OS film by dry etching techniques.Subsequently, the organic polymer film is patterned by conventionalmeans, as described earlier, using the patterned film as template.

[0102] Option d: The organosilicate film is sacrificial andphoto-defmable.

[0103] The OS film is exposed and developed, as described earlier, andthis pattern is transferred into the OS film by dry etching techniques.Subsequently, the organic polymer film is patterned by conventionalmeans, as described earlier, using the patterned OS film as a template.After the organic polymer film has been patterned, the OS film isremoved by dissolving in an acid or by dry etching or by chemicalmechanical polishing

[0104] If the global planarizing step has been omitted previously, thisstep can now be introduced into the flow. This step is recommended butnot essential in the process sequence. Once the pattern has beentransferred into the organic polymer film, conventional plug fillingtechniques can be applied to make the interconnect.

EXAMPLES Example 1 Fabrication of Single Level Damascene Structures

[0105] SiLK-I semiconductor resin was spin coated onto a 200 mm Siliconsubstrate to form a layer approximately one micron thick. The coatingwas cured on a hotplate at 325° C. for 1.5 minutes and in a furnace at400° C. for 30 minutes. Next, CYCLOTENE 4022-35 photodefinable BCB basedresin was spin coated onto the SiLK-I resin layer. The BCB formed auniform, good quality coating on the SiLK-I coating with no wettingdefects. The BCB layer was then exposed to a UV source to pattern it,developed and cured using the recommended photodefinition steps forCYCLOTENE 4022-35 BCB based resin.

[0106] The defined pattern was then etched into the SiLK-I coating usinga nitrogen/oxygen-based plasma. After etching, the BCB hardmask remainedpresent on the SiLK-I coating demonstrating fairly good etchselectivity. Next, the wafer was metallized using plasma vapordeposition. First, a thin layer (200 A) of titanium was sputterdeposited followed by sputter deposition of a thick copper film. At thispoint, the wafer was annealed for 1 hour at 400° C. to mimic a typicalcopper anneal. Lastly, the copper remaining on the surface of the BCBhardmask and the BCB hardmask were removed using a mild buffing cloth(cotton) and with mesitylene solvent. The result was removal of the topBCB/Ti/Copper layers but leaving the copper in the defined features.

Example 2

[0107] CYCLOTENE 7200 resin formulation was diluted to different solidslevels with mesitylene. These were then spin-coated onto cured 7000Angstrom (7000 A) thick SiLK-I resin films. The BCB was thenphotodefined using standard, recommended processes. The parts were thenetched using a nitrogen/oxygen plasma. The results, listed in Table 1,show the etch selectivity of 8:1 of this non-optimized etch process.TABLE I Etch Selectivity of Cyclotene Resin to SiLK Resin % Solids inPre-etch Post-etch Amount of Maximum BCB Hardmask Hardmask HardmaskEtched Etch Solution Thickness, Å Thickness, Å Å Selectivity 10 928 0928 7.5:1 15 3025 2150 875 8.0:1 20 8618 6550 2068 3.4:1 30 26680 255321148 6.1:1

Example 3

[0108] Vinyl triacetoxy silane (VTAS) was added to Dowanol PMA at 3.5percent and 10.0 percent by weight. The VTAS was hydrolyzed by adding 1mole water to 1 mole VTAS. Next, two bare silicon wafers werespin-coated with the two solutions and baked at 340° C. for one minuteunder a nitrogen blanket. The thickness of the VTAS layer, after thebake, was about 24.5 nm and 132 nm for the 3.5 percent and 10 percentsolutions, respectively.

[0109] Separately, additional wafers were prepared by spin coating 100mm silicon wafers with SiLK-I 550 dielectric resin and curing at 400° C.for 30 minutes. Using profilometry, the thickness of the SiLK layer wasabout 450 nm. The stock wafers were then covered with a low tack tape,such that only half of the wafer was exposed. Then the VTAS/PMA solutionwas spin-coated, the low-tack tape was removed, and the wafer was placedon a hot plate at 340° C. for 1 minute under a nitrogen environment. Theresult was half-coated wafers, one with the 3.5 percent solution and onewith the 10 percent solution.

[0110] These wafers were then exposed to nitrogen-oxygen plasma for oneminute. After the plasma treatment, the half of the wafer without theVTAS overlayer was completely etched. However, the SiLK resin with theVTAS hardmask was not etched at all. As a result, the etch selectivityof the VTAS hardmask to the SiLK resin was greater than 18:1 (450 nm orSiLK resin totally removed/24.5 nm of VTAS not completely removed).

Example 4

[0111] Additional wafers were coated with the SiLK-I 550 resin and curedas in Example 3. These wafers were then coated with 10 percent VTASsolution and again baked at 340° C. for 1 minute under nitrogen. Then asecond SiLK-I resin layer was spin- coated. The coating was ofacceptable quality. The wafer was then cured 5 times at 400° C. for 30minutes. No blistering, peeling or cracking was observed in the wafer,thereby demonstrating the sufficient thermal stability of this materialfor the application.

Example 5

[0112] An organosilane solution was prepared by adding 3.92 g ofvinyltriacetoxysilane (VTAS) and 1.13 g of phenyltrimethoxysilane (PTMS)to 95.15 g of Dowanol™ PMA. An equi-molar mass of water based on totalsilane content was added to the mixture and the solution was shakenovernight. The solution was filtered through a 0.1 um filter.

[0113] Approximately 3 mL of the resulting solution was applied onto a200 mm silicon wafer at 750 rpm. Immediately after dispensing thesolution, the wafer was accelerated at 10000 rpm/sec to 3000 rpm anddried for 30 seconds. After drying, the wafer was baked on a hot plateat 180° C. for 60 seconds. The thickness of the silane film was 152 A.

[0114] Approximately 3 mL of a SiLK™ I Semiconductor Dielectric solution(150 nm nominal film thickness) was applied at 60 rpm to the silanecoated wafer prepared above. Immediately after dispensing the oligomersolution, the wafer was accelerated at 10000 rpm/sec to 3000 rpm anddried for 45 seconds. After drying, the oligomer was further polymerizedon a hot plate at 320° C. for 90 seconds under a nitrogen blanket. Afterhot plate baking, the wafer was visually evaluated for defects. Minimaldefects were observed. The thickness of the SiLK dielectric film wasapproximately 1400 Angstroms (1400 A). The adhesion of the silane/SiLKstack on the silicon wafer was measured to be 0.27 MPa-m^(½).

[0115] Subsequent testing, including etch selectivity, on wafersprepared in manner similar to the preparation method stated above and inExample 6 revealed that the underlying organosilicate film may have beendamaged or partially removed during application of the subsequentoverlying dielectric layer. Various methods for avoiding such a problemmay include solvent selection for the spin formulation for the overlyingdielectric layer, selection of silane monomers to increase cross-linkingor uniformity of the organosilicate layer, method of manufacture of theorganosilicate material to increase uniformity of the layer (see e.g.Example 10).

Example 6

[0116] An organosilane solution was prepared by adding 4.9 g of 0.001 NHCl to 15.3 g of Dowanol PMA. The PMA mixture was placed in an ice bathand 1.7 g of PTMS was added while stirring. 18.3 g of VTAS was thanslowly added to the solution. The silane solution was shaken for 60minutes and then diluted to 14.8 wt % organosilane by adding 39.47 g ofthe solution to 93.30 g of Dowanol PMA. The solution was shaken for 5minutes and then allowed to equilibrate. The solution was then furtherdiluted to 10 wt % organosilane by adding 16.90 g of the 14.8% stocksolution to 33.11 g of Dowanol PMA.

[0117] Approximately 3 mL of the silane solution prepared above wasapplied onto an 200 mm silicon wafer surface at 750 rpm. Immediatelyafter dispensing the solution the wafer was accelerated at 10000 rpm/secto 3000 rpm and dried for 30 seconds. After drying, the wafer was bakedon a hot plate at 180° C. for 60 seconds. The thickness of the silanefilm was 310 Angstroms (310 A).

[0118] Approximately 3 mL of a SiLK I Semiconductor Dielectric solution(100 nm nominal film thickness) was applied to the silane coated waferprepared above at 60 rpm. Immediately after dispensing the oligomersolution the wafer was accelerated at 10000 rpm/sec to 3000 rpm anddried for 45 seconds. After drying, the oligomer was further polymerizedon a hot plate at 320° C. for 90 seconds under a nitrogen blanket. Afterhot plate baking, the wafer was visually evaluated for defects. Minimaldefects were observed. The thickness of the SiLK dielectric film wasapproximately 1080 Angstroms (1080 A).

Example 7

[0119] An organosilane solution was prepared as in Example 5 except thatno PTMS was added to the solution. Only VTAS was used as the silanecomponent. The nominal organosilane concentration (100% VTAS) was 4.5 wt%.

[0120] Approximately 3 mL of the silane solution prepared above wasapplied onto a 200 mm silicon wafer surface at 750 rpm. Immediatelyafter dispensing the solution the wafer was accelerated at 10000 rpm/secto 3000 rpm and dried for 30 seconds. After drying, the wafer was bakedon a hot plate at 180° C. for 60 seconds. The thickness of the silanefilm was 240 Angstroms (A).

[0121] Approximately 3 mL of a SiLK I Semiconductor Dielectric solution(100 nm nominal film thickness) was applied at 60 rpm to the silanecoated wafer prepared above. Immediately after dispensing the oligomersolution the wafer was accelerated at 10000 rpm/sec to 3000 rpm anddried for 45 seconds. After drying, the oligomer was further polymerizedon a hot plate at 320° C. for 90 seconds under a nitrogen blanket. Afterhot plate baking, the wafer was visually evaluated for defects. Massivefilm defects, particularly dewetted areas and film retraction, wereobserved. The thickness of the SiLK film was approximately 1170 A.

[0122] A series of wafers was then prepared as described above exceptthat the SiLK dielectric film thickness varied from 1170 A to 10400 A. Avisual scale was used to characterize the SiLK dielectric film qualitywith 10 representing very poor film quality (massive dewetting and/orretraction) and 1 representing excellent film qualtiy. The table belowgives the film quality and SiLK film thicknesses. The wafers describedin Examples 5 and 6 are included for comparison. This demonstrates thatfor thin overcoat films the compatibility of the overcoat with theunderlying layer appears more sensitive than for thicker overcoat films.Organosilane Film SiLK Film Wafer ID Thickness, A Thickness, A FilmQuality A 240 1170 10  B 240 1440 10  C 240 2560 5 D 240 3760 2 E 2405700 2 F 240 10400  2 Example 5 150 1440 2 Example 6 310 1080 2

Example 8

[0123] An organosilane solution was prepared as in Example 7 except thatthe fmal 10 organosilane concentration was 2.5 wt %.

[0124] A series of wafers were prepared as described in Example 7. Thetable below summarizes the film quality and thickness of these wafers.The wafers described in Examples 5 and 6 are included for comparison.Organosilane Film SiLK Film Wafer ID Thickness, A Thickness, A FilmQuality A′ 120-140 1170 10  B′ 120-140 1440 10  C′ 120-140 2560 1 D′120-140 3760 1 E′ 120-140 5700 1 F′ 120-140 10400  1 Example 5 150 14402 Example 6 310 1080 2

Example 9

[0125] This is an example of making a buried etch stop layer.

[0126] Approximately 3 mL of AP4000 Adhesion Promoter from The DowChemical Company was applied onto a 200 mm silicon wafer at 750 rpm.Immediately after dispensing the solution, the wafer was accelerated at10000 rpm/sec to 3000 rpm and dried for 30 seconds. After drying, thewafer was baked on a hot plate at 180° C. for 60 seconds.

[0127] The thickness of the silane film was 152 A. Approximately 3 mL ofa SiLK I Semiconductor Dielectric solution (400 nm nominal filmthickness) was then applied at 60 rpm to the adhesion promoter coatedwafer prepared above. Immediately after dispensing the oligomer solutionthe wafer was accelerated at 10000 rpm/sec to 3000 rpm and dried for 45seconds. After drying, the oligomer was further polymerized on a hotplate at 320° C. for 90 seconds under a nitrogen blanket. The coatedwafer was then cured in a vacuum for 30 minutes at 400° C.

[0128] Approximately 3 ml of the organosilane solution prepared inExample 6 was then applied onto the cured 200 mm wafer surface at 750rpm. Immediately after dispensing the solution the wafer was acceleratedat 10000 rpm/sec to 3000 rpm and dried for 30 seconds. After drying, thewafer was baked on a hot plate at 180° C. for 60 seconds. Approximately3 ml of a SiLK I Semiconductor Dielectric solution (100 nm nominal filmthickness) was then applied to the wafer at 60 rpm. Immediately afterdispensing the oligomer solution the wafer was accelerated at 10000rpm/sec to 3000 rpm and dried for 45 seconds. After drying, the oligomerwas further polymerized on a hot plate at 320° C. for 90 seconds under anitrogen blanket. After hot plate baking, the wafer was visuallyevaluated for defects. No visual defects were observed.

Example 10

[0129] This example demonstrates the advantages of using a combinationof different silanes.

[0130] An organosilane mixture was prepared by first adding 0.58 g of 1N acetic acid to 3.19 g of phenyltrimethoxysilane (PTMS). The PTMSmixture was placed in a water bath. 21.13 g of VTAS and 3.28 g ofdeionized water were simultaneously, continuously added to the stirredPTMS solution. The silane solution was stirred for 60 minutes and thendiluted to 14.1 wt % organosilane by adding 26.24 g of the solution to133.98 g of Dowanol PMA. This stock solution was shaken for 5 minutesand then allowed to equilibrate. The solution was then further dilutedto 4.2 wt % organosilane by adding 11.66 g of the 14.1 % stock solutionto 29.78 g of Dowanol PMA.

[0131] Approximately 3 mL of the diluted silane solution prepared abovewas applied onto a 200 mm silicon wafer surface at 750 rpm. Immediatelyafter dispensing the solution the wafer was accelerated at 10000 rpm/secto 3000 rpm and dried for 30 seconds. After drying, the wafer was bakedon a hot plate at 250° C. for 60 seconds. The thickness of the silanefilm was 913 Angstroms.

[0132] Approximately 3 mL of a SiLK I Semiconductor Dielectric solution(100 nm nominal film thickness) was applied at 60 rpm to the silanecoated wafer prepared above. Immediately after dispensing the oligomersolution the wafer was accelerated at 10000 rpm/sec to 3000 rpm anddried for 45 seconds. After drying, the oligomer was further polymerizedon a hot plate at 320° C. for 90 seconds under a nitrogen blanket. Afterhot plate baking, the wafer was visually evaluated for defects. Minimaldefects were observed. The thickness of the SiLK dielectric film wasapproximately 1080 Angstroms.

What is claimed is:
 1. A method comprising providing a substrate,forming a first layer on the substrate, wherein the first layer has adielectric constant of less than 3.0 and comprises an organic polymer,applying an organosilicate precursor over the first layer, wherein theprecursor is selected from the group consisting of curable polymersbased on (i) divinylsiloxane-bis-benzocylobutene and (ii) hydrolyzedproducts of at least one alkoxysilane or acyloxysilane, curing theprecursor to form an organosilicate resin removing a portion of theorganosilicate resin to expose a portion of the first layer, andremoving the exposed portions of the first layer.
 2. The method of claim1 wherein the substrate comprises an active substrate containingtransistors.
 3. The method of claim 1 wherein the organic polymer is apolyarylene.
 4. The method of claim 3 wherein the organic polymer is thereaction product of a cyclopentadienone functional compound and anacetylene functional compound.
 5. The method of claim 1 wherein thefirst layer is porous.
 6. The method of claim 1 wherein theorganosilicate resin is a cured reaction product ofdivinylsiloxane-bis-benzocyclobutene monomers.
 7. The method of claim 1wherein the organosilicate resin is a cured product of hydrolyzedalkoxysilanes, hydrolyzed acyloxysilanes, or a combination thereof. 8.The method of claim 1 wherein the organosilicate resin is photodefinable.
 9. The method of claim 8 wherein the step of removing aportion of the organosilicate resin comprises exposing theorganosilicate to activating wavelengths of radiation to causepolymerization reaction where exposed and removing the unexposedportions of the organosilicate with a suitable developer.
 10. The methodof claim 1 wherein the portions of the first layer are removed byetching.
 11. The method of claim 10 wherein etching comprises RIE typeof plasma etch using oxygen, nitrogen, helium, argon, C_(x)F_(y),C_(x)H_(y)F_(z), C_(x)H_(y), W_(x)F_(y) or mixtures thereof.
 12. Themethod of claim 1 wherein the step of removing a portion of theorganosilicate comprises applying a photoresist over the organosilicate,exposing a portion of the photoresist to activating radiation,developing a photoresist to reveal a portion of the organosilicate, andetching the organosilicate.
 13. The method of claim 12 wherein theetching step comprises RIE type of plasma etch using oxygen, nitrogen,helium, argon, C_(x)F_(y), C_(x)H_(y)F_(z), C_(x)H_(y), W_(x)F_(y) ormixtures thereof.
 14. The method of claim 1 further comprising applyinga conductive metal in at least some of the regions where the first layerwas removed.
 15. The method of claim 1 further comprising adding asecond layer having a dielectric constant of less than 3.0 over theorganosilicate resin, forming a patterned hardmask over the secondlayer, and etching the second layer.
 16. The method of claim 15 whereinthe etching comprises etching through the second layer to theorganosilicate material and, where the organosilicate was previouslyremoved, etching into the first layer.
 17. The method of claim 15wherein the second layer is applied and etched before the step ofremoving a portion of the organosilicate layer.
 18. The method of claim7 wherein the organosilicate resin is the cured reaction product ofhydrolyzed silanes and the silanes prior to hydrolysis comprise (a) analkoxysilane or acyloxysilane having at least one hydrocarbon groupattached directly to the Si atom which hydrocarbon group contains anon-aromatic, unsaturated carbon to carbon bond, and (b) an alkoxysilaneor acyloxysilane having at least one hydrocarbon group attached directlyto the Si atom which hydrocarbon group includes an aromatic ring. 19.The method of claim 18 wherein the silanes further comprise (c) analkoxysilane or acyloxysilane having at least one C₁-C₆ alkyl groupattached directly to the Si atom.
 20. The method of claim 18 wherein thesilanes comprise (a) 50-95 mole % silanes of the formula

wherein Ra is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Ya is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl , C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, —SiZa₂ORa′, or—ORa′; Ra′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Za is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORa′, provided at least one of Za or the combination Ra—Ya comprises anon-aromatic carbon carbon bond unsaturation, (b) 5 to 40 mole percent

wherein Rb is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Yb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, -SiZb₂ORb′, or-ORb′; Rb′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Zb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORb′, provided at least one of Zb or the combination of Rb—Yb comprisesan aromatic ring, and. (c) 0 to 45 mole percent

wherein Rc is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Yc is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl a C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, —SiZc₂ORc′, or—ORc′; Rc′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Zc is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORc′, provided at least one of Zc or the combination of Rc—Yc comprisesan alkenyl.
 21. The method of claim 18 wherein the first silane (a) is avinyl acetoxy silane and the second silane (b) is an arylalkoxysilane.22. An integrated circuit article comprising an active substratecontaining transistors and an electrical interconnect structurecontaining patterned metal lines separated, at least partially, bylayers or regions having a dielectric constant of less than 3.0 andcomprising an organic polymer, wherein the article further comprises alayer of an organosilicate resin immediately above and in contact withat least one layer of the organic polymer material wherein theorganosilicate resin is the cured reaction product of a precursorselected from divinylsiloxane bis benzocylcobutene based oligomers andhydrolyzed products of at least one alkoxysilane or acyloxysilane. 23.The article of claim 22 wherein the organosilicate resin is thehydrolyzed product of silanes comprising (a) an alkoxysilane oracyloxysilane having at least one hydrocarbon group attached directly tothe Si atom which hydrocarbon group contains a non-aromatic, unsaturatedcarbon to carbon bond, and (b) an alkoxysilane or acyloxysilane havingat least one hydrocarbon group attached directly to the Si atom whichhydrocarbon group includes an aromatic ring.
 24. A compositioncomprising the hydrolyzed or partially hydrolyzed product of acombination of silanes comprising (a) an alkoxysilane or acyloxy silanehaving at least one hydrocarbon group attached directly to the Si atomwhich hydrocarbon group contains a non-aromatic, unsaturated carbon tocarbon bond, and (b) an alkoxysilane or acyloxysilane having at leastone hydrocarbon group attached directly to the Si atom which hydrocarbongroup includes an aromatic ring.
 25. The composition of claim 24 whereinthe combination further comprises (c) an alkoxysilane or acyloxysilanehaving at least one C₁-C₆ alkyl group attached directly to the Si atom.26. The composition of claim 24 wherein the first silane (a) is a vinylacetoxy silane and the second silane (b) is an arylalkoxysilane.
 27. Thecomposition of claim 24 wherein the combination comprises (a) 50-95 mole% silanes of the formula

wherein Ra is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Ya is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl , C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, —SiZa₂ORa′, or—ORa′; Ra′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Za is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORa′, provided at least one of Za or the combination Ra—Ya comprisesa.non-aromatic carbon carbon bond unsaturation, (b) 5 to 40 mole percent

wherein Rb is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Yb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, —SiZb₂ORb′, or—ORb′; Rb′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Zb is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORb′, provided at least one of Zb or the combination of Rb—Yb comprisesan aromatic ring, and (c) 0 to 45 mole percent

wherein Rc is C₁-C₆ alkylidene, C₁-C₆ alkylene, arylene, or a directbond; Yc is C₁-C6 alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl a C₆-C₂₀ aryl,3-methacryloxy, 3-acryloxy, 3-aminoethyl-amino, 3-amino, —SiZc₂ORc′, or—ORc′; Rc′ is independently, in each occurrence, a C₁-C₆ alkyl or C₂-C₆acyl; and Zc is C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂₋₆ alkynyl, C₆₋₂₀ aryl, or—ORc′, provided at least one of Zc or the combination of Rc—Yc comprisesan alkenyl.
 28. The use of the composition of claim 24 as an adhesionpromoter.
 29. An article comprising a first film which comprises thecured product of the composition of claim 24 in direct contact with asecond film comprising an organic polymer which comprises aromaticgroups and at least some non-aromatic unsaturated carbon to carbonbonds.
 30. A method of making the composition of claim 24 comprisingcontinuously adding over the course of the hydrolysis reaction one ofthe components to a solution comprising the other component wherein thecomponent to be continuously added is selected to be the more highlyreactive component in the hydrolysis reaction.
 31. The method of claim24 wherein water is also continuously added over the course of thehydrolysis reaction.